An object is a collection of properties. A property is a associate between a name and a value.

for...in can be used to iterate over all the enumerable properties of an object.

var myFan = {
    make: 'Honeywell',
    blades: 4,
    rotation: 'on'
}

for (var i in myFan) {
    if (myFan.hasOwnProperty(i)) {
        console.log(i + " :: " + myFan[i]);
    }
}
// outputs
// make :: Honeywell
// blades :: 4
// rotation :: on

Ways to create objects

Object initializers

var rectangle = {width: 10, height: 100};

Constructor function

function TV(make, model) {
    this.make = make;
    this.model = model;
}

var myTv = new TV('LG', 'ThinQ');

Object.create

Allows to choose the prototype object for the object you want to create, without having to define a constructor function.

var bike = {
    wheels : 2,
    gear: 6
}
var myBike = Object.create(bike);

References: